The present disclosure relates generally to electrical power distribution, and particularly to measurement of power for at least one of a plurality of circuits. A building owner of a multi-tenant building, where deregulation has taken effect, can often purchase power from a utility provider in bulk at a wholesale rate, and re-sell it to the tenants. A sub-metering panel allows the building owner to accurately measure & bill the tenants for the power consumed by each tenant.
Sub-metering is traditionally performed by installing a current transformer (CT) on the conductor that is carrying the electrical load. There is one CT per phase of any load that is to be monitored, and each CT has two wire leads that carry the signal from the CT to the meter. These CTs are space consuming and difficult to mount. They take up wire bend space within an electrical distribution enclosure, as defined by Underwriters Laboratories (UL), and are obstructions to wires and cables in the equipment gutters and wire ways. The installation of these CTs and the extensive internal wiring is a cumbersome, time-consuming process and therefore increases the expense associated with the installation process. Furthermore, while present CTs incorporated within circuit breakers are adequate for their intended purpose of powering and activating circuit breaker trip units, they typically lack an accuracy and external communication capability suitable for sub-metering purposes.
Another method of sub-metering is also known as modular metering. Modular metering involves installing a modular meter for each suite. This method is space consuming, as it requires a meter for each circuit to be monitored. Yet another method of sub-metering is also known as master metering. In this method of sub-metering, a building owner divides the total annual utility bill of the building by a predetermined factor, such as square footage, and number of tenants per suite, for example, and charges the suite's tenant a fraction of the total utility bill according to the predetermined factor. This method is highly inaccurate.
Accordingly, there is a need in the art for a sub-metering arrangement that overcomes these drawbacks.